Great strides have been made in the understanding of unstable angina and its relationship to the acute coronary syndromes and myocardial infarction during the last decade of the 20th century, Detailed information about ECG changes and serum cardiac markers, as well as the conclusions drawn from numerous large, randomized interventional trials can now be integrated into the traditional clinical picture. Clinicians can now classify patients into diagnostic and prognostic categories and can perform risk stratification with unprecedented precision. With this information, the decision to hospitalize patients and the selection of noninvasive or invasive evaluation and management strategies can be individualized for optimal outcomes.